For any bodies i, k, nhttp://roman-inkinen.front.ru/main_triangle.GIF
All constants positive, but const'(in) may be positive or negative.
Accelerations in equations (1), (2), (4), (5) are called gravitational accelerations
accelerations in equations (1), (2), (6), (7) are called Kulon accelerations

Law (1) is acceleration relation conservation law
a(ni)/a(in)=const(in): accelerations change in time, but acceleration relation does not change.
All equations containing constants are conservation
laws.
No mass, no force, no charge.
Excuse me for my english, I'm foreigner.